begging forgiveness ... It's not a ford problem but a difficult problem with the other brand...yes I have friends with Chevys

soStrange automotive electrical problem we need help with…

55 chevy automatic with 383 stroker motor, carbed, p/s,p/b,a/c

Dakota digital dash system including neutral safety switch and

Transmission gear indicator



When it is running right, it’s scary strong. Cruises nicely.

Problem… when cruising along the engine dies like you cut it off…BUT will start back up immediately and run perfectly till the next time it does it.
Might be 15 minutes…15 days or three month later. Might do it 4 times in a row or once and not repeat. Speed does not effect it. Engine temp does not effect it…
does it hot or cold. With the a/c on or off. It does not have a cutoff switch in the system. Longest period with no failure is 7 months… shortest was 4 minutes.

When it stalls we checked fuel by looking in the bowl of carb and gas is spraying as it should, so we are ruling out fuel problem.... we are assuming electrical of some sort. So far we’ve done the following…



Replaced battery with new red top optima battery and all new battery cables (2 gauge I think)
Replaced all ground cables frame/block… frame/chassis with 2/0 welding cable with new crimped connectors and clean, bare metal attachment points
Replaced ignition switch (twice… first with import then with oem switch)
replaced coil and distributor with MSD system with spark control box, separate coil and distributor…it was taken from running vehicle. It's doing the same thing as the original ignition system.
Replaced complete wiring harness…headlight to taillight with new Autowire harness…including all switches and relays. Professionally done.
Everything else electrical works without a glitch… we are at the wall here…

Ideas, suggestions, calculated wild a** guesses welcomed…

thanks

 

How is the Neutral safety switch set up on the DD? They have a couple of ways to configure it I believe either a manual switch or wired to the transmission. Have you checked the wiring on that to be 100% sure nothing is losing ground in that circuit anywhere. Have you bypassed the NSS?

Have you tried disconnecting the DD to see if the source is there? With the dash disconnected I am not sure how the NSS integrates but again you should be able to bypass it.

It sounds like the coil could be grounding out.

In general it sounds like there is a wire shorting somewhere and when it happens it's just momentary. Any vibration or bump could set it off anywhere in the harness.

When you say the car was totally rewired was that after an attempt to fix it or it happened after the wiring job. It sounds like you changed out your entire ignition system in an effort to fix this I assume. If that is the case go back and look at all the feeds that were existing that you connected to. The source of the problem could be somewhere before the connections to the ignition system.

Have you called MSD/Holley to troubleshoot the ignition system and distributor with you? I had a problem with my sniper and the worked through the troubleshooting wire by wire with me.

The challenge here is given how intermittent it is there is no way to tell if a change you made actually worked since it could take 7 months to show up again. Changing more than 1 thing at once can make it really hard to diagnose as you don't know if you compounded a problem.

 

One thing you could try is disconnect the tachometer lead from the coil.

 

answers in red

 

That's one thing we haven't tried... what is the logic behind that ??? loose connection at the coil ?

 

Just taking stab in the dark - is there an oil pressure safety switch or similar circuit that will cut the ignition or fuel that could be faulty?

 

The DD has one connector in the back of the gauge cluster on mine, but your version may be different. You could disconnect that. There is also one power and one ground wire that runs to the controller box from the fuse panel. You could disconnect those as well to be sure there is no power running through that system at all.

you still should be able to bypass the NSS. Without looking at the wiring I am not sure how to do it but I am guessing it is a 2 pin connector to the transmission that you could jump. The connection may also be on the controller box and you can jump it there?

 

Just me but I would temporarily install a voltmeter or 12 volt light under the dash and tempoarily connect it to the power wire feeding your ignition switch. (Use a battery disconnect when the car is not running.) Engine dies again, look to see if there is voltage. If your losing voltage there move the voltmeter/ light lead further upstream towards the fuse panel. If the voltage is not effected at those points try moving the connection down stream past your ignition switch. Just keep sampling at different connecting points til you get to the MSD unit or coil. Hopefully you will see the voltage drop at the same time the engine shuts down. Also check your IGN fuse. Hopefully no corrosion on the terminals getting hot with all the current an MSD needs. It could be a problem on the ground side of your MSD circuit too.
But this problem was there before the MSD was added right?

Is the battery grounded right to the engine block? It really should be then ground straps block to frame and block to fire wall/body sheet metal.

Just some ideas.

 

I don't think so but will put it on the list to check

 

Sounds like a Ground ?: Engine to Frame, Frame to Cab..... but I see that you replaced all.... still might wanna check

 

The logic is that a tachometer is hooked to the negative side of the coil, if that wire gets unintentionaly grounded through wiring or because of a fault in the tachometer it will kill the engine dead

 

When it dies you need to run a jumper from battery positive to battery positive on the coil. That eliminates all power possibilities.
edit
I reread your post and it starts immediately so my theory won't tell you squat

 

This is a likely culprit, since I assume it was there since the problem started, and is still there. Is the tach in the Dakota cluster or stand-alone? Digital or analog?

 

When the engine dies, does it also lose all electrical, or just the engine? Will lights, radio, heater, horn, etc., still work, or is everything totally dead but cycle back on when the key is turned? This would narrow it down to primary electrical feed, or just one circuit.

 

Just another thought. Inside the distributor check the breaker plate to distributor body ground strap. If one side is loose or sometimes the strap is partially broken next to a ring terminal on the end it could cause you wild intermittant problems like this especially as vacuum advance shifts the timing at part throttle.